Clay soils made up about half the 170ha dairy farm.
Farm manager Zac Haderbache said the soils dried out in summer, leaving the remaining peat soils to carry a disproportionate amount of the herd.
In the drought of summer 2008, the clay soils grew 3kg of dry matter (kg DM) a day for six weeks compared with 22kg DM a day from the peat soils.
However, even in a normal year, summer grass growth lagged behind that of the peat soils.
AgResearch scientist David Stevens estimated that benefits from irrigation and effluent nutrients could increase pasture growth on the clay downs by 20%.
Over a year, that would equal the annual 16 to 17 tonnes of DM produced on the peat soils.
He warned that effluent tended to be low in potassium.
Mr Haderbache, who was completing his first year running the farm, said there was potential to increase production.
However, he did not want to do it at the expense of cow condition.
"There has to be a balance," he said.
A dry season and loss of pasture production on the clay downs had a huge financial effect.
In 2006-07, the farm milked 500 cows and produced 190,000kg of milk solids (kg ms) but the drought last year meant 520 cows only produced 176,000 kg ms.
Mr Haderbache said the two soil types complemented each other as the peat soils were wet over winter and spring.
But increasing the summer performance of the clay downs was where an increase in production would come from.
He said milk production of 1200kg a ha or 400kg a cow was achievable, but he was not keen to compromise cow condition by increasing the present stocking rate of 3.2 cows a ha.
At that stocking rate, he grazed paddocks to leave a residual of 1500kg DM a ha.
Telford's farm director, Ian Knowles, said the neighbouring sheep and beef unit could be used more to help the dairy farm increase production and generate a greater return on capital.
The cows will spend winter on 27ha of the sheep unit for up to 11 weeks and be fed 13kg DM a head a day of kale and baleage.
Two leased run-off blocks of 14ha and 60ha were used to rear young stock.
This summer the run-offs carried 200 yearling heifers but next summer Mr Knowles expected them to carry 150 2-year-old and 150 rising 1-year heifers.
The run-offs contributed 140 tonnes of silage while 200 bales of baleage were made off the milking platform.
The Telford dairy farm was run by a sharemilker until last year when it was decided the polytechnic would own the cows and employ a manager.
It was going through a transition stage with the age and class of stock.
Artificial insemination was done over six weeks with 60% of the herd in calf, and then bulls were run with the cows for nine weeks.
Mr Haderbache said the empty rate was 8% this year.
The calving date for this spring has been pushed back six days to August 10, by which stage he hoped to have pasture cover of 2000kg DM a ha.
He said the Friesian-cross cows were bigger than he liked at up to 650kg.
He intended to breed them a bit smaller.
Monitoring the farm during the milking season was an important function.
Each week, Mr Haderbache walked the farm to measure pasture growth.
He also regularly tested the quality of pasture and effluent applied so he knew what was going on and what was being grown.
Monitoring also included monthly testing of the effluent pond.
The farm was involved in a trial on how cows reacted to nitrogen inhibitor Eco-N, but he said there was anecdotal evidence the cows favoured pasture which had been treated with the product.
Half the area of some paddocks had been treated and Mr Haderbache said cows appeared to graze the treated area harder than the non-treated area.
Pasture quality was always an issue for Mr Haderbache, but as the focus moved to improving pasture growth on the clay downs, Dairy NZ consulting officer Caroline Hadley provided figures which showed cows at Telford ate about 13,000 kg DM a ha of pasture.
A further 2500kg DM a ha was provided from bought-in supplements, silage, baleage and dry cow grazing.
Mrs Hadley said the New Zealand average was 12,000 tonnes, while cows at Lincoln University ate 15,000 tonnes.
She described Telford's production as "respectable" and highlighted the benefits of Mr Haderbache's monitoring.